Electric governor for prime movers



Nov. 17, 1959 J. 'r. LIEBEL 2,913,538

ELECTRIC GOVERNOR FOR PRIME MOVERS Filed ilay 26. 1958 V r 3 Sheets-Sheet 1 To Other EngineGovernar Frequency 1 Circuit f Fig. l Throttle Position and Reference 1 V 1 Magnetic Throttle Generator lA nplifler "2323 and Engine G V a. Electra-H d- Pump Filter raxlclfuigae 1 Throttle Preeeure Fl 2 sump Requlator 9 Output Currents to Colie Control Input Current 4- Frequency Fig.4 Fig.5

- Transient Steady State WITNESSES INVENTOR Q a John T. Liebel BY fi Applied ATTORNEY Nov. 17, 1959, J. T. LIEBEL ELECTRIC GOVERNOR FOR PRIME MOVERS 3 Sheets-Sheet 2 Filed May 26, 1958 AAAAL Nov. 17, 1959 J. T. LIEBEL ELECTRIC GOVERNOR FOR PRIME MOVERS 3 Sheets-Sheet 3 Filed May 26, 1958 'llll'lllllull" ll'll |-|.|.L ll'llllllllll United States Patent ELECTRIC GOVERNOR FOR PRIME MOVERS John T. Liebel, Amherst, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 26, 1958, Serial No. 737,674

' 15 Claims. (Cl. 290-40) This invention relates to electric systems of control including magnetic amplifiers, and more particularly to systems of control, for governing the operation of any mechanical load but as herein disclosed for governing the operation of a prime mover, or prime movers, coupled to drive electric generators, or sets of generators, as for example alternators.

The present trend particularly in military applications is to expect higher and higher performance from electric generating equipment. This trend has reached the point of necessitating higher performance from the prime movers driving the generating equipment. These higher performance requirements are essential needs and include, closer steady-state control of prime mover speed on mechanical loads and closer steady-state control of electric frequency of, say, an alternator driven by a prime mover, more reliable and effective load sharing among two or more generating units coupled to prime movers, and, especially, very rapid recovery from transient load changes, and to minimize frequency deviation andprovide for a faster recovery from transient load changes.

One broad object of this invention is the provision of accurate and reliable electric governing control means for the prime mover driving electric generating means.

Another broad object of this invention is the provision of means to hold a very close steady-state control of the frequency of an alternator coupled to a prime mover.

It 'is also'an object of this invention to use smaller and less expensive components and simpler circuitry than used heretofore and yet to obtain an overall equally high standard of performance than was possible to obtain heretofore.

I: is also an object of this invention to provide for interchangeable use of all components, or parts, regardless of the frequency output of the alternator or service application involved, as for example, service applications involving 15 cycles, 25 cycles, 50 cycles, 60 cycles or or 400 cycles, except, of course, for the particular components in the circuitry selected that are frequency responsive.

It is also an object of this invention to accomplish the desired functions without the use of tubes or other fragile components having a rather limited useful life but with the use of components which have a long useful life and which will withstand shock and vibration with no damage to its components.

It is also an object of this invention to provide a control signal for stabilizing the actuation of the throttle of jects and advantages will become more apparent from 2,913,588 Patented Nov. 17, 1959 a study of the following specification and the accompanying drawings, in which:

Figure l is a schematic showing, in block form, of the electrical elements of this invention;

Fig. 2 is a schematic showing, in block form, of the electro-hydraulic apparatus used with this invention; Fig. 3, consisting of portions 3A and 3B, is a diagrammatic showing of the electric apparatus and the prime mover to be controlled;

Fig. 4 shows the operating characteristic of the magnetic amplifiers used;

Fig. 5 shows some curves of value in understanding the frequency control of this invention; and

Fig. 6 shows the operating characteristic of a circuit used in this invention to obtain some very desirable operation hereinbelow explained.

To gain a broad understanding of this invention, a brief preliminary discussion of Figs. 1 and 2 may be helpful.

' The block designated Generator represents the alternator G mechanically coupled to the engine included in the block designated Throttle and Engine. The generator G is electrically connected to a load, not shown.

The throttle of the engine is actuated hydraulically by the Electro-Hydraulic Valve Actuator, which is in turn controlled electromagnetically by the output of the Magnetic Amplifier.

To provide for proper control of the engine throttle the Magnetic Amplifier is controlled as a function of the alternator frequency through the Frequency Circuit. To prevent hunting, and to otherwise improve operation, the Magnetic Amplifier is controlled by a feedback as a function of change of throttle position with respect to Throttle Position Reference.

When two alternators are operated in parallel through the Throttle Position Reference a control is also provided on the Magnetic Amplifier to provide for appropriate load sharing of the two alternators.

To provide the hydraulic control a suitable Pump, coupled to the engine through a suitable Gear Drive, pumps liquid through the Filter to the Electro-Hydraulic Throttle Actuator which efiects operation of the throttle. To provide for a proper constant liquid pressure in the system a Pressure Regulator bleeds off the proper amount of liquid from the Pump to the Sump.

To understand some of the details of this invention, reference may be had to portions 3A and 3B of Fig. 3.

The engine E is shown coupled to drive the alternator G which alternator is in use connected to supply power to leads L1, L2 and L3 and to the control apparatus.

, The alternator may be delta-connected or Y-connected but as shown is a Y-connected machine having the outer terminals of its phase windings 1P, 2P and SP connected to the load leads L1, L2 and L3, respectively. A transformer T2 has its primary windings P1, P2 and P3, as shown, connected across windings 1P, 2P and 3P, respectively. The secondary windings S1, S2 and S3 of transformer T2 are, as shown, connected to the three-phase full-wave rectifier assembly CR2 connected, as shown, to thus provide a twelve-volt, direct current output on leads 1 and 2 for the frequency inverter FI. A capacitor C7 aids in producing a substantially constant direct current voltage of twelve volts across leads 1 and 2 for the remaining and essential portions of the frequency inverter circuitry. The voltage source may be a battery or any other source.

The frequency inverter circuitry includes a pair of switching devices TR1 and TR2 connected to the leads :1 and 2. In this arrangement, each of the devices is in the form of a three electrode semiconductor device commonly referred to as a transistor.

The construction and function of transistors are well (z 2 known in the art, but for a more detailed discussion of transistors as applied to the circuitry here shown, reference may be had to the United States Letters Patent No. 2,273,384 of Richard 1.. Bright et a1.

The transistors here used are of the P-N-P junction type and the electrical and magnetic characteristics of the parts, as the resistors R6 and R8, the starting capacitor C2, and the electromagnetic windings and the core, and the capacitor C3, are all so chosen that an alternating current of approximately l000 cycles per second of near square wave form appears on terminals 12 and 17.

The main windings 13 and 18 of the magnetic amplifier MA1 and the main windings and 19 of magnetic amplifier MAZ are thus supplied with an alternating current of 1000 cycles and constant voltage regardless of the frequency output of the generator G. This means the units responsive to the frequency inverter may be used in any application regardless of the frequency of the generator involved. In other words, the benefits of the highfrequency magnetic amplifier and other units are available and may be used interchangeably with generators supplying either 15 cycles, cycles, 50 cycles, 60 cycles or 400 cycles.

Further, if a constant voltage direct current source of energy is available, as from a storage battery, the transformer T2 and the rectifiers CR2 are not needed. It suffices to have an output from an inverter of 1000 cycles per second and a voltage of 8 volts, for the main windings of the magnetic amplifiers.

The engine is controlled by the throttle T, which is actuated by link LK from the throttle actuator TA. The throttle actuator includes a piston P in the cylinder Cy. Liquid under a suitable constant pressure enters conduit CO and thus provides a liquid pressure at both sides of the piston P through the system of conduits shown.

of the piston P depends on the positions of the valves 101 and 102 with respect to the discharge openings adjacent the bottom ends of the valves. The valves are actuated by push-pull electromagnets having the actuating coils 14 and 16. These coils are in the output circuits of the magnetic amplifiers MA1 and MAZ, respectively. The input to the main windings of the magnetic amplifiers is as shown provided from the alternator G, through the frequency inverter Fl above discussed.

The energizing circuits for the mainzwindings may be traced from lead 12, when lead 12 is positive, through the main winding 13 of magnetic amplifier MAL rectifier CR6, actuating coil 14-, and rectifier CR9, to the conductor 17. When lead 12 is positive, a circuit is also established through the main winding 15 of magnetic amplifier MA2, the rectifier CR11, actuating coil 16, and rectifier CR8 to the lead 17.

characteristics areas near the same as possible. Further, the straight portion of the characteristic is preferably quite steep but not actually vertical.

To cause each magnetic amplifier to operate at or near the midpoint as point a of its characteristic, the magnetic amplifiers are provided with bias windings. The bias windings are energized from the rectifier CR1. The alternating current terminals of rectifier CR1 are connected Whether or not the pressure is the same on both sides directly across phase 3P, but may be connected to any source of alternating current energy of suitable voltage. The important feature is that a source of constant direct 7 current voltage is available on leads 28' and 33.

positive conductor 28 through resistor R4, adjustable re sistor R12, the bias balance adjustable resistor R11, the bias windings 37 and 38 of the magnetic amplifierMAZ to negative conductor 33. Since the adjustable resistors R12 and R11 are in the circuits of the biasing windings, these resistors can be used to adjust the bias level, i.e., the up-and-down position on the magnetic characteristic of both magnetic amplifiers may be adjusted, as for example to the dotted lines appearing in Fig. 4. Since the relative amount of resistances of the resistors R12 and R11 in the respective circuits of bias windings 31 and 32, and 37 and 38 is adjustable, it is apparent that a decrease ofresistance in the circuit of the bias windings 31 and 32 Will'efiect an increase in resistance in the circuit of the bias windings 37 and 38. Of course, the reverse effect is caused by a reverse operation of the adjustable resistor R11. 7

From the discussion of the circuitry and control of the bias windings it is apparent that the operations of the nected to energize several potentiometer circuits.

utility of the potentiometer circuits will become apparent magnetic amplifiers may be adjusted to any level on the operating characteristic and that balanced operation may be obtained at the levels selected.

The output terminals of rectifier CR1 are also con- The , winding is connected in a loop circuit with a reactor L,

When lead 17 is positive, a circuit is established through rectifier CR5, coil 14, rectifier CR10, and the main Winding 18 of magnetic amplifier MA1 to conductor 12, at the same time a circuit is also established from conductor 17, through rectifier CR12, coil 16, rectifier CR7 and the main winding 19 of magnetic amplifier MA2 to the conductor 12.

From the foregoing, it is apparent that the outputs of having a selected reactance value, a series connected capacitor C4, having a selected capacitance value and the alternating current terminals of rectifier CR3 as shown.

A second capacitor C3 having a selected capacitance value is connected in parallel to the reactor L and capacitor C4.

The circuitry just described, assuming particular circuit parameters for the capacitors C3 and C4 and the reactor L, is for a -cycle output of transformer T1. When the application calls for a SO-cycle output of transformer saturating type, the true effective function of coils 14 and, i

T1, then capacitor C4 is disconnected from junction] 1 and the lower terminal of capacitor C5, suitable for 50 cycles, is connected to junction J1. If the alternator frequency is still some other value, the circuit parameters 'of' elements L, C3, and C4 have to be changed to suit.

The direct current output terminals of the full-wave rectifier CR3 are connected across resistor R19. The connection is such that the negative terminal is connected to conductor 133 and the positive terminal is connected to lead 39 to which the upper junction of the resistor R19 is also connected. The operating characteristics of the elements CR3, L, C3, C4 and the windings of'transformer T1 are so selected that the voltage impressed across leads39 and 133 is rather accurately and sensitively substantially inversely proportional to frequency over. a given range which includes the desired operating frequency of the alternator G. A rise of frequency from a selected value causes a decrease in voltage across leads 39 and 133 and a decrease injfrequency from a selected value causes a rise involtage across leads 39 and 133.

A full-wave rectifier CR4 is also connected across phase 3P. The circuit for this rectifier CR4 maybe traced from L3 through the resistor R10, the alternating current terminals of rectifier CR4 and ground lead GL to junction I. A filter capacitor C6 is connected directly across the alternating current terminals of rectifier CR4. The direct current terminals of the rectifier CR4 are connected in a loop circuit including the frequency reference potentiometer R7, and the resistor- R9 to the negative conductor 133.

As is apparent from the connections of full-wave rectifier CR4 heretofore explained and the showing in Fig. 3A, the positive terminal of rectifier CR4 is connected to junction 46 to which the lower junction of frequency reference potentiometer R7 is also connected. Since the positive potential at lead 39 is sensitively and accurately variable as a function of the minutesttendency of a change of frequency and the positive potential of junction 46 is fixed, the voltage across resistors R7 and R9 thus constitutes a reference voltage. It is apparent that lead 45 may be so positioned on resistor R7 that the voltage drop across leads 39 and 45 will be a function of such minute tendency of a change of frequency.

From explanations made hereinbefore, it is apparent that the voltage drop through resistors R7 and R9 is from positive to negative to junction 133. This means that tap 45 on potentiometer R7 is positive with respect to junction 133. Since junction 39 is positive with respect to junction 133, it is apparent that when the output-voltage of rectifier CR4 is constant, which is true for allnormal operation of the alternator, and the frequency and voltage output are constant, that tap 45 may be shifted to such a point on resistor R7 that tap 45 has the same positive voltage value as conductor 39. Shifting tap 45 merely means that curve CV may be shifted up or down as required. If the alternator frequency is at the desired value, say 60 cycles, and the alternator voltage is at the desired constant value, then the voltage value across junctions 39 and 133 will be, for example, at d on curve fV. By shifting tap 45, the curve CV is shifted until it includes point d. See Fig. 5.

In practice, this is accomplished by shifting tap 45 in such a direction until the voltage across leads 39 and .lead or tap 45 is zero. Thereafter, any departure of the frequency from the desired frequency will shift the direct current voltage across lead 39 and tap 45 along curve fV. If the frequency increases, lead 39 will have a lower voltage than lead 45 and when the frequency dechanges, have but a small effect, but if there is such a,

change the outputs of the rectifiers CR3 and CR4 are affected substantially alike. The output from secondary rectifier CR4 during a decrease in voltage will shift curve CV to position CV, but the output of rectifier CR3 will shift curve fV to fV. The difference voltage is still zero since point d is still at the same frequency value represented by point d.

By providing the magnetic amplifiers with control windings responsive to a selected portion of the voltage drop across leads 39 and 45, a control is provided as a function of the minutest tendency of a departure of the frequency of the alternator from a selected value. A minute tend ency to a change of the frequency of generator G with respect to a selected reference frequency suflices to produce a voltage drop across leads 39 and 45. A control 6 effect may thus be produced in the magnetic amplifiers before there is any appreciable change in speed of the prime mover. A change in throttle position may thus be effected before there is a noticeable speed change to, counteract the speed change tendency.

There are some very important functions of this circuitry that should be pointed out. When there is a rapid, or transient, change of alternator output voltage, as there will be when there is a rapid change of load, then curve CV (see Fig. 5) moves substantially in time with such rapid voltage change. There is substantially no time delay and the change is a function of the instantaneous load on the alternator.

The inherent characteristics of the frequency responsive portion of this circuitry, in view of the necessary inclusion of reactors and capacitors in this portion of the circuitry, is such that its output lags the output of the reference voltage. The angle of lag may be asmuch as This means, if a rapid rise in load on the alternator takes place, that curve CV substantially instantly changes to position CV, and as much as 180 later curve fV changes to position fV. During the interim curve CV is in the CV position and curve fV moves to its new position fV', point d moves down toward the right along curve V. The resulting transient action is thus in a direction to give speed change anticipation. When there is a rapid dumping of alternator load point d, of course, moves up and to the left on curve fV. Again the speed change is anticipated.

For this electric governor the response is thus very fast, and the governor is load responsive without actually having to measure the power output of the alternator.

In practice, lead 45 is adjusted to such a position on R7 that there is no voltage across leads 39 and 45 when the frequency of the generator G is just right. If for any cause there is a slight change in the frequency in such a direction that lead 39 becomes more positive than lead 45 then an energized circuit is established from lead 39 through the frequency gain adjusting resistor R18, conductor 40, control windings 41 and 42 of magnetic amplifier MAI and control windings 43 and 44 of magnetic amplifier MA2 to lead 45. If the speed change is such that lead 45 is more positive than lead 39, then the control effect of the control windings 41, 42, 43 and 44 is, of course, in an opposite sense in the respective magnetic amplifiers.

It is, of course, understood that when the lead 39 is more positive than lead 45, then the control effect in magnetic amplifier MAl is in one sense and the control effect in magnetic amplifier MA2 is in an opposite sense, and when the lead 45 is more positive than lead 39, the control effects in the magnetic amplifiers MAI and MA2 reverses. The efl ect is thus a push-pull control on the actuating coils 14 and 16.

A governor control that takes into account frequency changes only may have an excessive drooping frequency versus load characteristic and may hunt, or manifest other minor instabilities, or both. To eliminate such not quite perfect operation, a throttle position feedback control is provided for the magnetic amplifiers.

To accomplish this control a throttle position selecting potentiometer R14, is connected across leads 28 and 33 and a throttle position indicating potentiometer R13 in series with resistor R3 is also connected across leads 28 and 33.

The feedback control is then effected by the circuit For the moment disregarding adjustable resistor R17 and the capacitor C9 in parallel with it, any movementpf the throttle and'thus tap 64 from the desired position unbala'nces'the voltage across taps 57 and 64 and causes a current to flow in the control windings 59, 60, 61 and 62 in this-feedback circuit'in such a direction to provide a negative push-pull feedback effect. In other Words, when tap 57 is more positive than tap 64, then current flows in the direction of the circuit above traced producing a negative feedback, and when tap 64 is more positive than tap 57, then the effect on the respective magnetic amplifiers' is reversed but the feedback is still a negative pushpull feedback. 7

To still more readily understand some particular novel features of this invention, reference may be had to a somewhat similar prior art electric governor for prime movers, disclosed and claimed in the pending application ofJohn T. 'Liebel and James E. Frederick, filed December 20, 1957, Serial No. 704,095, and entitled Electric Governor for Prime Movers.

The throttle position potentiometer R13 energizes the magnetic amplifier throttle position feedback windings 59, 60, 61 and 62 through the position feedback gain potentiometer R16 and the position reference potentiometer R14 as hereinabovelexplained. With this control circuit and the others already discussed, the system would be reasonably stable for steady-state operation, but in goingrapidly from a no-load condition on the generator G to a full-load condition on the generator G, or for any lesser rapid transient change, the governor would possess droop since the frequency sensing circuit, namely control windings 41, 42, 43 and 44 would be bucking the throttle position feedback circuit, namely windings 59, 60, 61 and 62. This droop is proportional to load. It is desirable to remove thedroop. Some preliminary discussion of the pertinent electrical theory at this point may be helpful.

As already mentioned, the tap 64 on potentiometer. R13 is mechanically coupled-to the throttle actuating linkage. This potentiometer R13 with the current limiting resistor R3 forms two legs ofca'Wheatstone bridge. The voltage divider potentiometer R14 forms two additional legs for this bridge. This bridge is connected as shown to the direct current output terminals of the rectifier CR1.

From this circuitry, it is apparent that any change in throttle position will result in a change of potential. between taps 57 and 64, all else remaining constant, that is, disregarding adjustable resistor R17 and capacitor Cfi.

To eliminate droop and improve stability, the primary interest is not so muchthrottle position but the rate of change of the throttle position. Since the primary interest liesin the rate of change of throttle position rather than in the measured throttle position, some means must be provided for blocking the DC. level. Capacitor C9 provides this function. Thus, the rate of charging and discharging of the capacitor is a measure of the rate of change of throttle position. Since the capacitor C9 is in parallel to potentiometer R17 and in series with the potentiometer R16 and the control windings 59 and 60, and 61 and 62, a signalinversely to the normal position signal is provided to the control windings. If the proper value .of capacity is chosen,- the necessary stabilizing signal isobtained.

Some investigation of the effect of the capacitor C9 reveals that obtaining the proper stabilizing signal is not quite as simple as juststated and that some dis advantages must beovercome.

Some comments on these disadvantages [will further the The current thenis equal to the difierential of'the charge on thecapacitor with respect to time, or

dq Z d? The instantaneous charge, q, on the capacitoris equal to the productof the capacitance and the applied voltage, or

( q and since the signal is an A.C. signal q=CEm sin'wt Therefore, since d. (4) z (CEm SID wt) Therefore,

(5) i=w CEm .cos wt From Equation 5, itis apparent that not only does the magnitude of the change in potential affect the magnitude of the currentbut the rate of change or frequency also has a bearing. This is desirable to the extent that the, greater the tendency towardcinstability (rate of throttle movementlthe greater, theinverse, or stabilizing, signaL'.

There is, however, a disadvantage and this lies in the fact 1 that a capacitor having a relatively large capacitance is needed.

As, suggested; hereinabove, it is undesirable to measure theactual position ,of, the throttle, that is, to obtain a; The reason for this isas follows: Since the throttle position sigsteady signal proportional to throttle position.

where i t/RC 6 equals the base of the'natural logarithms;

-t equals time in seconds;

E equals the magnitude of the potential in volts;

R' equals the sum of the resistance in the circuit in ohms;

and C equals the capacitance in farads.

When a' large displacement of the throttle occurs, such as the application or rejection of a large percentage of the rated load, a transient occurs within the circuit which. obeys the log Equation 6 given above. During the periodof the transient, a current again proportioned to. Equation6 will flow in the feedback windings. Due to the relatively large value of the capacitance necessary for capacitor C9, the time constant of the decay of the feedback transient is undesirably long. Since this inverse current signal is suflicient to cause a frequency error during its period and since the magnitude and time constant of the error are proportioned not only by the resistance. and capacitance but to the voltage change as well (because the interest is'in a specific current flow rather than a percentage of the maximum) some means of overcoming this characteristic must be added in order to ob-.

tain the high standard of performance expected of this. electric governor.

The elimination of the second disadvantage is the function ofthe non-linear impedance circuit network formed, by the adjustable -resistor"R15"and the diodes D1 and The current resulting D2 The diodes are connected in parallel with each other and poled in opposite sense with respect to resistor R15 connected in series with the parallelly connected diodes. This circuitry including the resistor R15 and the two diodes D1 and D2 is connected in parallel to the series circuit including the resistor R16 and the control windings 59 and 60 of magnetic amplifier MA2, and control windings 61 and 62 of magnetic amplifier MAl.

The function of the components discussed in the preceding paragraph in relation to the rest of the control is as follows. Let the assumption be that a large engine load transient has occurred resulting in a corresponding large throttle displacement and thus a fairly large feedback signal. During the transient, the voltage across capacitor C9 will be large, that is, the applied voltage will be large, resulting in a maximum current flow. Since the resistor R15 and the diodes D1 and D2 are connected in series with the capacitor C9, it is apparent that the large transient cur-rent, regardless of whether the current is a charging current or a discharging current, is shunted across the control windings 59 and 60, and 61 and 62. Due

to the non-linear characteristics of the diodes-the diodes provide an effective means of bypassing the large undesirable feedback transients and yet permit the control circuitry to function normally during steady stateconditions. This non-linear characteristic of this circuitry, shown in Fig. 6, thus allows the frequency responsive circuit, that is, control windings 41 and 4 2, and 43 and 44, a free hand so to speak when a correction signal ismost needed and to shift back to normal operation when the correction has been made. The effect is substantially equivalent to an on-oif control of the damping required for stabilization, turning the damping off when it would be undesirable, as during a transient, and back on during steady-state operation. 1

For effecting the operation of two, or more, generators in parallel, the voltage divider circuit, consistingof resistor R8 and potentiometer R28, is connected as shown. This connection is across the same bridge as previously described, and the voltage drop across this voltage divider circuit will thus reflect any change in throttle position and will thus provide a signal as a function of generator load. Any change in throttle position will then result in a voltage appearing across the 'voltage divider circuit. This voltage is applied to the control windings of the magnetic amplifier by a circuit that may be traced from tap 57 through conductor 158, control windings 75 and 76 of magnetic amplifier MAZ, control windings 77 and 78 ofmagnetic amplifier MAI, conductor 79, the upper contacts of the paralleling switch S, control windings 278 and 277, and control windings 276 and 275 of the respective magnetic amplifiers of the second unit, the voltage divider circuit VDC of the second unit, the lower contacts of the paralleling switch S, conductor 74 to tap 73 on the potentiometer R28. I

Two, or more, engine governors connected in this manner are so connected that the voltage effects are bucking. As long as these voltages, and therefore the throttle positions, remain equal, the net current flow in the magnetic amplifier control windings 75, 76, 77, 78, 278, 277, 276 and 275 will be zero. Any change in one voltage in one voltage divider circuit with no change in the others will cause a current flow, the elfect of which will be to equal the voltages through appropriately repositioning of the throttles. Thus, load sharing on an isochronous basis is achieved.

To briefly summarize some of the advantages of this invention, it is to be noted that the control:

(11) Has a very fast response.

(b) Is not sensitive to voltage changes of more than transient duration.

(0) Is not affected by throttle linearity (altitude, B.t.u.

fuel content, fouled plugs, etc.)

(4) Is less than A the volume of prior art controls.

(e) Is half the cost.

(f) Eliminates current and potential transformers of.

former similar governors. (g) Requires no wattmeter circuitry, the governor is not sensitive to phase load, and power factor.

. (h) Operates at a decreased power level.

While but one embodiment of the invention has been disclosed, it is to "be understood that the invention is capable of various adaptations which all fall within the spirit of the invention.

I claim as my invention:

1. In an. electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electrom'echanical means for effecting the operation of the throttle, magnetic amplifier means of a relatively high frequency type for energizing the electromechanical means, means for energizing the magnetic amplifier means from terminals energized with an alternating current of relatively high constant frequency, control means, operable as a function of the frequency of the alternating current output of said alternator, for controlling the operation of the magnetic amplifier means, second control means responsive to throttle position with reference to a selected position for providing a negative control effect on said magnetic amplifier means, and third control means for the magnetic amplifier means for providing a transientpositive control effect responsive to rate of change of throttle position from a prior position on said magnetic amplifier means.

2. In an electrical system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover at a predetermined frequency, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means for effecting theoperation of the throttle, high frequency type magnetic amplifier means for energizing the electromechanical means, means for energizing the magnetic amplifier means at a constant high frequency, control means, operable as a function of a frequency variation of the alternating current output of said alternator from said predetermined frequency, for controlling the operation of the magnetic amplifier means, control means responsive to throttle position with reference to a selected position for providing a negative control effect on said magnetic amplifier means, and further control means responsive to the rate of change in throttle position with reference to a selected position for providing a transient control effect on said magnetic amplifier.

3. In an electric system of control for controlling the speed of a prime mover, the combination of, a throttle for the prime mover, electromagnetic means for effecting the actuation of the throttle to thus control the speed second circuit means including rectifying means also con nected to the generating means for producing a direct current voltage as a function of frequency, third circuit means including a frequency inverter connected to the I alternator, magnetic amplifier means having its load windings connected to said inverter and connected to energize said electromagnetic means, said magnetic aim plifier" means having a control winding energized b'y a direct current that is proportionalto the difference between the voltage of the reference signal and'the-voltage as a function of the frequency of the alternating current generated by the generating means coupled to'the prime mover, control means responsive to the throttle position for producing a negative feedback effect in themagnetic amplifier and control'means, responsive to'therateof change of throttle position with reference to aprior throttle position, for producinga transientpositive feedback effect in the magnetic amplifier means.

4. In an electric system of control for controlling ;the speed of a prime mover, the combination of, athrottle for the prime mover, electromagnetic means for effecting the actuation of the throttle to:thus control the speed of the prime mover in accordance with the energization of said electromagnetic lmeans, said prime mover in use being coupled to generating means for generating an alternating current of a selectedvoltage and frequency, circuit means connected to said generating means for producing a direct current voltage inversely proportional to any change in the frequency of the alternating current generated by said generating means, a source of" direct current voltage of a constant value, mixing circuitry for said direct current voltage inversely proportional :to changes in frequency and said direct current voltage of constant value to provide an output as a function of the difference of said direct current voltages, a

source of high frequency voltage, high frequency type magnetic amplifier means having its output windings energized from said source of high frequency voltage and connected to energize said electromagnetic means,

'said magnetic amplifier means having control windings energized by said direct current voltage outputof said mixing circuitry, said magnetic amplifier means also having control windings energized as a function of throttle position to produce a negative feedback effect in the magnetic amplifier means and having further control windings, responsive to rate of change of throttle position relative to a prior throttle position, for producing a transient positive feedback effect in the magnetic amplifier means.

5. In an electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover for controlling the speed of the prime mover with reference to a seleeted constant speed, electromechanical means for effecting-the operation of the throttle, a source ofhigh frequency alternating current voltage, magnetic amplifier means connected to said source for energizing the electromechanical means, control means, operable as afunction of the frequency of the alternating current output of said alternator, for controlling the operation of the magnetic amplifier means, second control means respon sive to throttle position with reference to a selected position for providing a negative control effect on said magnetic amplifier means, third control means responsive to the rate of change of a transient voltage for providing a positive control effect on said magnetic amplifier'means as'a function of the rate of change of the throttle p'sition with reference to a prior throttle position, a second electric system of control and apparatus to be controlled as'hereinbefore recited, and further control means responsive to the difference of the throttle positions of the two systems for controlling the relative effects of the two magnetic amplifier means involved to balance theloads on the two alternators.

6. In an electric system of control for maintaining frequency of the alternating current output of an alternator coupled to a prime mover at a predeterminedfrequency, in combination, a throttle for the prime mover to 'changethe speed of the prime mover, electromechan ical means for etiectingithe operation of the throttleto change the prime mover speed, a source of high fre-" quency constant voltage alternating current, magnet c amplifier means connected to said source for energizlng' the electromechanical means, control'm'eans for providing a reference signal as a function of the frequency variation of the alternating current output of said alternator from said predetermined frequency for controllingthe operation of the magnetic amplifier means, further control means responsive to the rate of change in throttle position with reference to a prior throttle position for providing a transient positive feedback control effect on said magnetic amplifier means, a second electric system" of control and apparatus to be controlled as hereinbe fore recited, and still further control means responsive to the difference of the throttle positions in the two systems for controlling the relative effects of the two mag netic amplifier means involved to balance the loads of the two alternators.

7. In electric control apparatus for controlling the operation of a prime mover, said control apparatus including an alternating current generator coupled to the prime mover, isolation transformer meansconnected to the generator, rectifying means, connected to'the generator, for producing a constant voltage direct current output, LC circuitry including rectifying means, connected -to the transformer means, for producing a direct cur-' rent output voltage highly sensitive to the minutest change in frequency of the generator, the combination of a control member for said prime mover, electromagnetic means for controlling the position of said control member to thereby control the operation of said prime mover in accordance with the energization of said electromag.-' netic means, asource of high frequency alternating current, electrical amplifier means having main windings energized from said source of high frequency and having its output connected to energize said electromagnetic means, control means connected to both of said rectifying means for controlling said electrical amplifier means I as a function of the voltage difference between the constant direct current voltage and the frequency sensitive direct current voltage to thus effect energization of said electromagnetic means in accordance with said voltage difference, control means responsive to throttle position for producing a negative feedback in the magnetic am-' plifier means, and further control means responsive, to

the rate of change of throttle position with reference to v a. prior throttle position, for producing a transient positive feedback as a function of'throttle position.

8. In an electric system of control for maintaining.

the frequency of the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means for effecting the operation of the throttle, magnetic amplifier means of a relacontrol effect on said magnetic amplifier means, said third control means comprising an adjustable impedance and a capacitor connected in parallel thereto connected in series with the second control means for providing a transient positive control effect, responsive to the rate of change of the throttle position with reference to a bination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover,'

ing current output of said alternator, for controlling the operation of the magnetic amplifier means, second control means I including control windings responsive to. throttle position with reference to a selected position for providing a negative control effect on said magnetic am-- plifier means, and third control means for the magnetic:

amplifier'means, comprising an adjustable resistor and a capacitor connected in parallel thereto connected in series with the control windings of the second control means and a resistance circuit having a non-linear resistance characteristic connected in parallel to the control windings of the second control means, for providing a transient control effect, responsive to the rate of change of the throttle position with reference to a prior position, on-said magnetic amplifier means.

- 10. In an electric system of control for maintaining the frequency of'the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means for effecting the operation of the throttle, magnetic amplifier means for energizing the electromechanical means, means for energizing the magnetic amplifier means from terminals energized with an alternating current of a substantially constant frequency, control means, operable as a function of the frequency of the alternating current output of said alternator, for controlling the operation of the magnetic amplifier means, second control means including control windings responsive to throttle position with reference to a selected position for providing a negative control effect on said magnetic amplifier means, and third control means for the -magnetic amplifier means, comprising an adjustable resistor and a capacitor connected in parallel thereto connected in series with the control windings of the second control means and a circuit, including a resistor and a pair of oppositely poled parallelly connected diodes connected in series with the resistor, connected in shunt rela tion to the control windings of the second control means.

11. In an electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover for controlling the speed of the prime mover with reference to a selected constant speed, electromechanical means for effecting the operation of the throttle, a source of alternating current voltage, magnetic amplifier means connected to said source for energizing the electromechanical means, control means, operable as a function of the frequency of the alternating current output of said alternator, for controlling the operation of the magnetic amplifier means, second control means including control windings for the magnetic amplifier means responsive to throttle position with reference to a selected position for providing a negative control elfect on said magnetic amplifier means, third control means for the magnetic amplifier means comprising an adjustable resistor and a capacitor connected in parallel thereto connected in series with the control windings of the second control means, responsive to the rate of change of a transient voltage for providing a transient positive control effect on said magnetic amplifier means as a function of the rate of change of the throttle position with reference to a prior throttle position, a second electric system of control and apparatus to be controlled as hereinbefore recited, and further control means responsive to the difierence of the throttle positions of the two systems for controlling the relative effects of the two magnetic amplifier means involved to balance the loads on the two alternators. Y

12. In an electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover constant, in combination, a throttle for the prime mover for controlling the speed of the prime mover, with reference to a selected constant speed, electromechanical means foreifecting the operation of the throttle, a source of alternating current voltage, magnetic amplifier means connected to said source for energizing the electromechanical means, con

trol means, operable as a function of the frequency of parallel thereto connected in series with the control wind in'g's' of the second control means and a circuit, including a' resistor and a pair of oppositely poled parallelly' connected diodes connected in series with-the resistor; con-- nected in shunt relation with the control windings of the second control means, responsive to the rate of change of a transient voltage for providing a transient positive control effect on said magnetic amplifier means as a function of the rate of change of the throttle position with reference to a prior throttle position, a second electric system of control and apparatus to be controlled as hereinbefore recited, and further control means responsive to the difference of the throttle positions of the two systems for controlling the relative efiects of the two magnetic amplifier means involved to balance the loads on the two alternators.

13. In an electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover at a selected frequency, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means for efiecting the operation of the throttle to change the prime mover speed, high frequency type magnetic amplifier means having control windings, and having main windings for actuating the electromechanical means, means for energizing the main windings of the magnetic amplifier means from terminals energized with an alternating current of relatively high constant frequency, first control means, including means providing an output signal that varies inversely to changes in frequency and including means for providing a reference signal that varies inversely to variations of the alternating current output voltage of said alternator, for controlling the energization of the control windings to thus control the operation of the magnetic amplifier means, said frequency responsive means including capacitive and reactive impedance means that provide a transient lag, during rapid changes in load on the alternator, in signal output with reference to the signal output of said voltage responsive means, and second control means responsive to rate of transient changes in throttle position for providing a further transient feed back control effect as a function of the rate of change of throttle position from a prior position on said magnetic amplifier means.

14. In an electric system of control for maintaining the frequency of the alternating current output of an alternator coupled to a prime mover at a selected frequency, in combination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means for effecting the operation of the throttle to change the prime mover speed, magnetic amplifier means having control windings,

and-having main windings for actuating the electro-' mechanical means, means for energizing the main wind-- ings of the magnetic amplifier means from terminals energized with'an alternating current of a selected constant frequency, control means,.including frequency responsivemeansproviding an output signal that varies inversely with changes in frequency of the alternator and including voltage responsive means. for providing a reference signal that. variesinversely with variations of the.

alternating current output voltage of said alternator, for controlling the energization of the control windings to thus control the operation of the magnetic amplifier means, said frequency responsive means including means that provide a transient time lag in output response with reference to the output of the voltage responsive. means.

15. In an electric system of control, for maintaining the frequency. of the alternating current output. of, an alternator coupled too. prime mover at a selected frequency, incombination, a throttle for the prime mover, which throttle in use is operable to change the speed of the prime mover, electromechanical means, for effecting the operation of the throttle to change the prime mover speed, magnetic amplifier means having control windings,

and having main windings for actuating the electromechanical means, means for energizing the main windings-of the-magnetic amplifier means from terminals} 1 energized with an alternating current of a selected. con stant frequency, control means, including frequency re-. sponsive means for providing an output signal which inl herently lags the change in alternator voltage-by a phase? angle and the magnitude of which signal variesrinverselyw to changes in frequency of the alternator coupled to, the prime mover and including means for providing an out-: putsignal substantially in time with changes in voltage of said alternator coupled to the prime mover and'whose.. magnitude varies inversely with changes of the voltage; output of said alternator, whereby a combined output. signal is supplied to the control windings of the magnetic; amplifier means that is a function of an anticipation of a;

change in frequency and to a change in frequency'for controlling the operation of said magnetic amplifier;

means.

References Cited in the file of this patent UNITED STATES PATENTS Helmick et a1. Dec. 20, 1955,, 

